The present invention relates to a universal device, provided with means to be controlled by a control unit which forms art of a projector. The device in conjunction with this control nit can be used inter alia for the automatic adjustment of the projector.
A standard CRT projector comprises three cathode ray tubes: one red, one green and one blue. Each of these cathode ray tubes is provided with projection means, which direct the light from these cathode ray tubes to a common screen. Three separate pictures are formed in this way, each in a different colour, which are superimposed on the screen. To obtain a good and clear picture on the screen, the different colours must be coordinated with one another. When a red, blue and green line are projected onto the screen, a white line can be seen on the superimposed picture when these three lines impinge exactly on each other, in other words when the convergence is well adjusted.
Many systems have been devised to improve the accuracy of the convergence adjustment.
First of all there is a manual adjustment system, as described for example in U.S. Pat. No. 4,672,275. In this, a reference picture provided with a number of reference points is projected onto the screen. A test picture which looks like the reference picture is projected onto this. This test picture is provided with a number of adjustment points, each corresponding to one of the reference points. In addition, a correction part is provided which corresponds to a given part of the reference picture. The correction part is a partial collection of the adjustment points. On carrying out the convergence adjustment, an adjustment point is selected within the correction part. The position of the selected adjustment point is altered with respect to the corresponding reference point. At the same time and proportionally, the positions of the other points within the correction part are also altered. As a result, the convergence of the correction part is built up in relation to the corresponding part of the reference picture. The correction data are stored in a large RAM.
This manual adjustment is very labour-intensive and time-consuming. Many potentiometers need to be set and moreover these frequently interact. It therefore follows that one requires a high level of knowledge to optimally adjust the equipment.
U.S. Pat. No. 4,999,703 describes a device for automatic convergence adjustment of a projector. Convergence correction is executed automatically, even during the operation of the projector, faults occurring as a result of drift in the electronic and mechanical components of the projector being eliminated. A test pattern for each of the primary colour pictures is projected onto a screen and the light reflected by the screen is scanned by a scanning system. The positions where the light sensor of the scanning system detects the test pattern for each of the primary colours are stored in a memory. These positions are then processed to determine correction values for the convergence of the primary colour pictures, in order to obtain convergence over the whole screen. A disadvantage of this method is that complete pictures are stored in the memory. For this purpose, large, and therefore expensive, memories are required.
U.S. Pat. No. 5,345,262 also describes a method and device for automatic convergence adjustment. In accordance with the method described therein, a test pattern is generated consisting of a row of discrete pattern units each of which has a contour and a central area, a variation in the illumination intensity appearing between the contour and the central area of the pattern unit. The test pattern is projected by each of the cathode ray tubes of the system. A row of light-sensitive elements is arranged so that they pick up the light from the test patterns that has been reflected by the screen. The position of each of the pattern units of a first projected test pattern is compared with the positions of the corresponding pattern units of the other projected test patterns. A number of error signals are generated and these are then used to control the cathode ray tubes so that the position of one of the test patterns is displaced in relation to the other such that the size of the error signals is reduced.
In accordance with a characteristic of the method described in the abovementioned American patent, the positions of different pattern units are compared by determining the centre of the slightly varying illumination intensity of each of the projected test patterns and comparing this with the position of the centres of the illumination intensity of the other test patterns.
A disadvantage of this is that a complete picture is sampled, which requires large memories, so-called frame memories. Frame memories are large memories that are able to store a complete picture. These are expensive and, in addition, time is lost during the adjustment process by looking for those locations where the test patterns have been displaced in relation to each otherxe2x80x94thus where the convergence is not well adjusted.
The convergence adjustment takes place in the said patent by calculating central points. This calculation is background-sensitive, and in some cases (for example with a blurred picture) can lead to incorrect results. If the central points are adjusted on top of one another, the eye will not necessarily view this as the correct convergence adjustment.
Another disadvantage of the adjustment method described therein and the corresponding adjustment equipment is that only the convergence can be adjusted. For complete adjustment of a projector, the geometry, focus, astigmatism, contrast modulation and gamma correction must also be adjusted in addition to the convergence. All these adjustments have a mutual influence on each other.
In the method and equipment described in U.S. Pat. No. 5,342,262, the intensity of the background light is measured and stored once only. This has the disadvantage that during the further adjustment process fluctuations in the background light are not taken into account.
In U.S. Pat. No. 5,091,733, U.S. Pat. No. 5,231,481, EP-A-0 616 473, EP-A-0 498 659, U.S. Pat. No. 5,497,054 and U.S. Pat. No. 5,432,404, devices with specific applications are described for automatic adjustments of projectors. All these named publications are based on test pattern generators being specifically present, which ensure the generation of a pre-defined pattern unit or units. The associated adjustment methods are based on the presence of the generated test pattern and its shape (for example discrete light points etc.).
These said publications all deal with devices with specific applications which execute only a limited number of adjustments automatically, demands frequently being made on the hardware used and on the underlying hardware which ensures actual controlling. There are thus publications which are based on the fact that a filter is included for the camera used, and that there is no connection between different control zones and different adjustments per se, that the hardware is synchronized with the analog signal coming from the camera, and that the measurement results are absolute, etc. Other publications make demands on the camera used: the resolution of the camera must be sufficiently high, in some cases the camera must be set up so that it is itself movable, and/or the complete picture must be sampled, requiring the presence of large memories.
Not one of the abovementioned publications provides suitable solutions for obtaining rapid adjustments using a universal device in a broad range of projectors, irrespective of the control hardware itself. Besides, the devices described in the aforementioned patents (applications) are not able to fulfil any tasks other than the adjustments of the projectors. They cannot serve as a peak detector, as a signal decoder, as a RAM expansion, for signal testing and analysis, or for wire-free transfer of information, without anything needing to be altered on the device.
It is an object of the invention to solve the aforementioned disadvantages relating to the convergence control using a universal device, and also to automate other adjustments, without sacrificing the universal character of the device according to the invention.
It is likewise an object of the invention to apply relevant automatic adjustments to projectors which are not of the CRT type, without in so doing changing the described methods.
The universal device, in accordance with the present invention, has the advantage that the same device can provide different adjustments for a projector, in accordance with the command signals sent by the control unit of the projector to the device.
The same device can also be used for other applications, possibly even outside the projector applications.
A universal device, in accordance with the invention, is provided with means intended to be controlled by a control unit which forms part of a projector. The device exhibits different operational characteristics in accordance with different applications imposed on it by the control unit. The device comprises the following components:
an analog-to-digital converter,
a memory,
a programmable digital component and
an interface to the control unit of the projector.
The device is universal. This means that the device is not responsible for just one task but, for each task where it is used, it is put into another operating state or mode by the control unit.
The universal device may also have an application imposed via an external control unit, for example via the control unit of a PC. This external control unit then sends its command signal or its command signals to the control unit which forms part of the projector, serves as a gate, and transmits the command signal or command signals to the universal device.
The projector, the control unit of which controls the universal device, may be a CRT projector, an LCD projector or any similar light valve projector.
Preferably, the analog-to-digital converter of the universal device is an 8-bit converter.
The memory is a high-speed RAM in each case. According to a preferred embodiment, the memory is a small memory. The expression small memory is to be understood as a small memory in terms of the prior art. With the progression of technology, ever larger memories are being manufactured. Therefore, it is possible that what is now regarded as a small memory will in a few years no longer be on the market and that what is now described as an average or even large memory will, within a few years, form part of what is now regarded as a small memory.
In contrast to the methods and equipment known from the prior art for the automatic adjustment of projectors, in every case for the present invention it is not necessary to have a memory sufficiently large to store the information of a complete picture. A typical value for the memory used in the universal device is, for example at this time, 32K, where a frame memory has a size of the order of 256K.
Using this small memory has the advantage that the universal device according to the invention, whenever use is made of the automatic adjustment system for a projector, is cheaper than the adjustment devices which are known from the prior art without accuracy and efficiency being lost.
According to yet another preferred embodiment, the universal device has a plug with a pin to which an analog signal can be applied. The signal is ultimately responsible for the analog-to-digital converter. This plug can be a separate plug, to which, for example, an analog signal originating from a camera can be applied. However, it can also form part of the interface to the control unit of the projector.
Again, according to another preferred embodiment, there are no means to ensure hardware synchronization with the analog signal applied to the pin. This means in fact that, for example, a PLL is superfluous which again makes the universal device cheaper. The presence of a PLL is not required when the data are sampled at a much higher frequency than the analog signal bandwidth.
The aforementioned universal device can be used for adjusting one or more of the following controls to a picture projected onto a screen by a projector: convergence, geometry, focus, astigmatism, contrast modulation and gamma correction.
Adjustment of the convergence means that the different colours which are projected onto the screen are aligned with each other.
When adjusting the geometry it can be investigated, inter alia, whether or not the projected straight lines exhibit a degree of curvature (xe2x80x98bowxe2x80x99 or xe2x80x98pinxe2x80x99) and whether or not lines which should be horizontal or vertical on the screen have a degree of slope (xe2x80x98skewxe2x80x99 or xe2x80x98keyxe2x80x99).
When focusing it is ensured that the image of a pixel projected on the screen is sufficiently sharp, for example in a CRT projector it is ensured that the electron beam correctly impinges on the faceplate (=the screen of the picture tube).
Astigmatism is the phenomenon which occurs, inter alia, on account of the fact that the electron beam in a picture tube does not intersect the faceplate orthogonally. As a result, the virtual pixel (or spot) that is thus formed is deformed elliptically. This elliptical deviation should be removed for optimal projection performance (sharpness).
In contrast-modulation adjustment, the intensity of each of the three projected colours is controlled separately in the same manner, to compensate for losses caused by light loss resulting from projection distance and lens effects. In this way a flat intensity curve is obtained ideally which means that there is as much light in the middle as the edges.
Gamma correction has to be carried out because colour is dependent on different control factors, including a non-linear relationship between the light and the incoming signal.
The universal device in accordance with the invention can also be used to adjust soft edge and adjacent and/or overlapping geometry (edge matching) in pictures being projected onto a screen using a minimum of two projectors (this is in addition to the adjustment of the aforementioned controls that can be carried out independently on each of the projectors).
Soft edge must be adjusted when a picture that is built up on the screen via one of the projectors exhibits an overlapping zone with a picture which is projected onto the screen by one of the other projectors. Soft edge adjustment is the adjustment of the intensity of both the pictures in this overlapping zone. In this process, the intensity of one picture in the overlapping zone must be slowly decreased while the intensity of the other picture in the overlapping zone must be slowly increased.
Adjustment of the adjacent geometry is the adjustment of the geometry of pictures which are projected adjacent to each other by two projectors (perhaps with a small overlapping zone in which soft edge is adjusted).
Overlapping geometry adjustment is the adjustment of the geometry of pictures projected on top of one another via two projectors.
The aforementioned adjustments can be carried out on one or more CRT projectors, LCD projectors or light valve projectors.
The universal device can also be used for other applications, for example for video digitization, as a peak detector, as RAM expansion, as co-processor for the control unit, as test configuration, for light communication between a minimum of two projectors and for signal decoding, for example for teletext decoding.
Another aspect of the present invention is a projection system which is provided with the aforementioned universal device. The projection system has a screen, a projector and a camera. The projector is provided with at least one picture-forming means that generates a picture, at least one projection means in order to project that picture onto the screen and a control unit. The camera is linked to the projector and views the picture or pictures which is/are projected onto the screen. This supplies an analog signal that is applied to the pin of the universal device. The control unit of the projector establishes the said device in a set mode after which it is able to execute tasks sent by the control unit and on the command of the control unit.
In order to carry out the adjustment methods described below, the colours of the projector must be switchable. Sometimes adjustment is only carried out on one of the colours at a time and sometimes a plurality of colours is needed at the same time.
According to a preferred embodiment of the invention, the camera, which is linked to the projector in the projection system, is a low-resolution camera. If the associated adjustment software is powerful enough, the price of the hardware can thus be reduced.
The camera may be a monochrome or a colour camera.
In accordance with another preferred embodiment, the camera is connected immovably to the projector.
It is not necessary for the camera to view the whole picture projected onto the screen, as long as it can view the locations where the effect of an adjustment to be carried out is visible.
The invention also provides methods for the automatic adjustment of all the aforementioned controls which can be carried out on the pictures which have been built up on a screen using at least one projector.
A first method which can be implemented using the universal device is one for the automatic adjustment of the convergence of at least two pictures, each of which has covered a different light path and which are built up on a screen using a projector. This projector is provided with a control unit and hardware responsible for convergence control. A camera linked to the projector views the pictures projected onto the screen and transmits a signal corresponding to the viewed picture to the control unit. According to the method, the pictures projected onto the screen are split into one or more adjustment zones. These adjustment zones do not necessarily have to be a matrix layoutxe2x80x94they may overlap. In the remaining part of the present document, the term xe2x80x98zonexe2x80x99 is the location where a particular control has the most effect. The coordinates of the adjustment zone or zones, as viewed by the camera on the screen, are fetched. This fetching operation for the coordinates may consist either of measuring the coordinates on the screen or, once they have been measured and written to a memory, of reading in the coordinates from the said memory or of the said coordinates being input by a user. The pictures that are projected onto the screen are viewed using the camera and form an analog signal which is converted into digitized values via an analog-to-digital conversion. The geometry of the projected pictures is not important as long as for each of the pictures to be adjusted the picture information more or less corresponds and is useful. The picture information, for example, can be for one picture the letter xe2x80x98Ixe2x80x99 and for the other picture the letter xe2x80x98Txe2x80x99. The picture information is then useful (the vertical lines of both letters can be adjusted on top of each other), and it more or less matches (both letters are not the same, but nevertheless have a part that corresponds: the vertical line). Even the intensity of both pictures does not have to be the same, as long as both pictures are visible. Using the digitized values a mathematical model can be constructed. Preferably, the mathematical model reproduces the effect of the convergence control in a specific adjustment zone on all other zones linked to this zone if the picture to be adjusted has been split into more than one zone. The relative distance between the pictures to be adjusted relative to one another in the adjustment zone or zones is determined by correlation of the digitized values.
Control signals are derived from the relative distance thus obtained and are sent to the hardware, which is responsible for the adjustment of the convergence in the adjustment zone or zones.
Another possibility for the application of this method is that the mathematical model, as calculated using the digitized values, can be written to a non-volatile memory. In a subsequent automatic convergence adjustment, this model written to memory is used as a starting point. The new measured digitized values are entered into the model, and if necessary the model is adapted on the basis of these.
The mathematical model, the mathematical model for the convergence adjustment as well as the mathematical models which will be disclosed below, can also calculate and model the chromatic aberration of the lensxe2x80x94the so-called xe2x80x98prismxe2x80x99 effect.
The method given below is provided for the automatic adjustment of the geometry of a picture which is built up on a screen using a projector. For this, the projector is provided with a control unit and hardware responsible for the adjustment of the geometry. A camera linked to the projector views the screen. The picture which has been projected onto the screen is split into one or more adjustment zones. These zones do not have to be in the form of a matrix, they may overlap each other. Reference values for the geometry are fetched (measured, read in from a memory or input by a user). The camera views the projected picture and generates an analog signal that is converted into digitized values via an analog-to-digital conversion. The geometry of the projected picture is not important as long as the picture information is useful and more or less corresponds to the reference values. The term xe2x80x98more or less corresponds toxe2x80x99 has the same meaning as in the case of convergence. A mathematical model is constructed using the digitized values. This mathematical model preferably reproduces the effect of one adjustment zone on all the other zones linked to this adjustment zone if the projected picture was split into more than one adjustment zone. The relative distance between the reference values and the picture, which is to be adjusted to the reference values, in the adjustment zone or zones is determined by correlation. From this relative distance, signals are derived which are sent to the hardware responsible for the geometry control concerning the adjustment zone or zones.
Likewise, the model as calculated using the digitized values may be written to a non-volatile memory. When a subsequent automatic adjustment is made to the geometry, this model written to memory is used as a starting point. The newly measured digitized values are entered into the model and if necessary the model is adapted on the basis of these.
The method given below is provided for the automatic adjustment of adjacent and/or overlapping geometry of pictures which are built up on a screen using at least two projectors. For this, the projectors are each provided with a control unit and hardware responsible for the control of adjacent and/or overlapping geometry. One or more cameras linked to the projectors view the screen. The pictures which have been projected onto the screen are split into one or more adjustment zones. These zones do not have to be in the form of a matrix, and can overlap each other. In addition, the projected pictures do not have to be test patterns as understood in the prior art: any picture can be used on the condition that the picture information is useful and more or less corresponds. The coordinates of the adjustment zone or zones, as viewed on the screen by the camera, are fetched (measured, input by the user or read in from a memory). The projected pictures are viewed using the camera or cameras and form an analog signal that is converted into digitized values via an analog-to-digital conversion. A mathematical model is constructed using these digitized values. Preferably this mathematical model reproduces the effect of an adjustment zone on all the other zones that are linked to this adjustment zone if the pictures have been split into more than one adjustment zone. Correlation is used to determine the relative distance between the pictures undergoing adjustment in the adjustment zone or zones. Signals are derived from this relative distance which are sent to the hardware responsible for the control of adjacent and/or overlapping geometry concerning the adjustment zone or zones.
Here too, as has been described above, the model can be written to a non-volatile memory where it is stored for later use for the automatic adjustment of adjacent and/or overlapping geometry.
A method for the automatic adjustment of the focus of a picture, built up on a screen using a projector, the projector being provided with a control unit and hardware responsible for focus control and a camera, linked to the projector, being used to view the screen, is provided, comprising the following steps. Firstly, the picture, projected onto the screen, is split into one or more adjustment zones. These adjustment zones need not necessarily be in the form of a matrix and may overlap each other. As adjustment of focus takes places on only one colour at a time, the picture information only has to be useful so that the methods described below give sufficient information. The coordinates of the adjustment zone or zones, as viewed on the screen by the camera, are fetched (measured, read in from a memory or input by a user). The camera views the picture projected on the screen and this forms an analog signal that is converted into digitized values via an analog-to-digital conversion. The digitized values are used in the construction of a mathematical model. Preferably, the mathematical model reproduces the effect of focus control in a specific adjustment zone on all the other zones linked to this zone if the picture to be adjusted has been split into more than one zone. The relative values for the optimum focus value of the adjustment zone or zones are determined and signals are derived from these relative values for the optimum focus value, which signals are sent to the hardware responsible for the focus control concerning the adjustment zone or zones.
According to a preferred embodiment of the method for the automatic adjustment of the focus, the relative value for the optimum focus value is determined by calculating the variance on the basis of histograms.
According to another preferred embodiment of this method, the relative value for the optimum focus value is determined by spectrum evaluation.
By using spectrum evaluation a choice may be made between different forms of optimum sharpness observed by the user. It is for this reason that optimum focus value is referred to.
Thus one may want a pixel that has little xe2x80x98flairxe2x80x99, that is the pixel has little low light intensity at the edges or it may be, for example, wide in the low light intensities and narrow in the high light intensities.
In this case as well, the model can be written to a non-volatile memory. On a subsequent focus control, the parameters of the model are fetched so that the model does not have to be constructed again on the basis of digitized values.
The following method is provided for the automatic adjustment of astigmatism of a picture which is built up on a screen using a projector. For this, the projector is provided with a control unit and hardware responsible for the control of astigmatism. A camera linked to the projector views the screen. The picture projected onto the screen is split into one or more adjustment zones, which need not be in matrix form and which may overlap. The coordinates of the adjustment zone or zones, as viewed on the screen by the camera, are fetched (measured, read in from a memory or input by a user). As adjustment of astigmatism takes place on only one colour at a time, the picture information only has to be useful so that the method described below gives sufficient information. The projected picture is viewed by the camera, and this forms an analog signal which is converted into digitized values via an analog-to-digital conversion. These digitized values are used to construct a mathematical model which preferably reproduces the effect of the astigmatism control in a specific adjustment zone on all other zones linked to this zone if the picture has been split into more than one zone. The relative measures for the astigmatism are determined from the digitized values and from these relative measures signals are derived which are sent to the hardware responsible for astigmatism control concerning the adjustment zone or zones.
According to a preferred embodiment, the relative measures for the astigmatism are determined by calculating the variance on the basis of histograms.
According to another preferred embodiment, spectrum evaluation is used to determine the relative measures for the astigmatism.
According to yet another preferred embodiment, the relative measures for the astigmatism are determined using moment evaluation.
As described previously, the model can also in this case be written to a non-volatile memory for later use.
The method, which according to the invention is provided for the automatic adjustment of the contrast modulation of a picture which is built up on a screen using a projector, consists of the following steps. The projector itself has a control unit and hardware responsible for the control of contrast modulation. A camera linked to the projector views the screen. Calibration values for the colour of the picture are fetched for the camera. The picture projected onto the screen is split into one or more adjustment zones, which do not necessarily have to be in matrix form and may overlap each other. The coordinates of the adjustment zone or zones as viewed by the camera on the screen are fetched (measured, read in from memory or input by a user). As the adjustment of contrast modulation takes places for only one colour at a time, the picture information only has to be useful. Useful information is pictures which possess slowly varying intensity variations (slow with reference to the measurement rate) so that, using the method described later in this document, sufficient information can be extracted for intensity adjustment, for example a uniform picture. The projected picture is viewed by the camera, and forms an analog signal which is converted into digitized values via analog-to-digital conversion. The digitized values are used to construct a mathematical model. Preferably this reproduces the effect of the contrast-modulation control in a specific adjustment zone on all other zones linked to this zone if the picture has been split into more than one adjustment zone. A measurement for the relative intensity is determined and from this signals are derived which are sent to the hardware responsible for the contrast-modulation adjustment concerning adjustment zone or zones.
The model can be written to a non-volatile memory for later use where it may be fetched for a subsequent contrast-modulation control.
A method for the automatic gamma-correction adjustment of a picture which has been built up on a screen using a projector also forms part of the present invention. The aforementioned projector is provided with a control unit and hardware responsible for gamma-correction control. A camera linked to the projector views the screen. The method consists of the following steps. Firstly, calibration values for the camera are fetched for the colour of the said picture. The picture projected onto the screen is split into one or more adjustment zones which need not be in matrix form and may overlap one another. The coordinates of the adjustment zones, as viewed by the camera on the screen, are fetched (measured, read in from a memory or input by a user). As gamma-correction adjustment takes place only on one colour at a time, the picture information only has to be useful. Useful information is pictures which possess slowly varying intensity variations (slow with reference to the sampling rate), so that, by using the method described later in this document, sufficient information can be stored for gamma-correction adjustment, for example a uniform picture. The camera views the picture projected onto the screen and this forms an analog signal, which is converted into digitized values via analog-to-digital conversion. The digitized values are used to construct a mathematical model. If the picture to be adjusted has been split into more than one zone, this mathematical model preferably reproduces the effect of a specific adjustment zone in all the other zones linked to it. A measure of the relative intensity is determined and from this signals are derived which are sent to the hardware responsible for gamma-correction concerning the adjustment zone or zones.
Instead of constructing a model on the basis of digitized values, it can also be fetched from a memory on the condition that it has been written thereto during a previous gamma-correction control.
The following method is provided for the automatic adjustment of soft edge, for pictures which are built up on one or more screens using at least two projectors, each provided with a control unit and hardware responsible for soft edge control, one or more cameras linked to the projectors viewing the screen or screens. Calibration values for the colour of the pictures are fetched for the camera or cameras. The pictures projected onto the screen or screens are split into one or more adjustment zones, which need not be in matrix form and which can overlap each other. The coordinates of the adjustment zone or zones, as viewed by the camera on the screen, are fetched (measured, read in from a memory or input by the user). As adjustment of soft edge occurs only on one colour at a time, the picture information only has to be useful. Useful information is pictures which possess an intensity variation which varies slowly in terms of time (slow is with reference to the sampling rate) so that, using the method described later in this document, sufficient information can be stored for soft-edge adjustment, for example a uniform picture. The pictures projected onto the screen or screens are viewed using at least one camera and these form an analog signal which is converted into digitized values via analog-to-digital conversion. The digitized values are used to construct a mathematical model. If the picture to be adjusted has been split into more than one zone, this mathematical model preferably reproduces the effect of a specific adjustment zone on all other zones which are linked to this zone. A relative intensity measure is determined and from this signals are derived which are sent to the hardware responsible for soft-edge adjustment concerning the adjustment zone or zones.
In this case as well, the model constructed using the digitized values may be written to a non-volatile memory and can be fetched for a subsequent soft-edge adjustment.
In accordance with a preferred embodiment, in each of the abovementioned methods digitized values are added to the digitized values measured. This can occur by interpolation in the time domain or in a frequency domain and also by filtering in the frequency domain. The addition of digitized values introduces an updated, longer series of digitized values.
According to another preferred embodiment, a transformation is carried out on the digitized values. Transformation means both a transformation from the time domain to another domain as well as the inverse transformation from the other domain to the time domain. According to a preferred embodiment, the transformation is a Fourier transform, that is to say a transformation to the frequency domain.
Preferably all the aforementioned methods use linked zones, the said mathematical model each time reproducing the effect of the control corresponding to the method in a specific adjustment zone on all other zones linked to this adjustment zone since adjacent zones exert an effect on each other. Thus if a specific zone were to be adjusted, the previously adjusted zone would no longer be correctly adjusted due to electrical, optical and mechanical effects. In the case of linked zones, two or more zones are adjusted at the same time, as a result of which the mutual effect can be taken into account by the construction of a mathematical model. This has the result that all types of projectors can be adjusted by the aforementioned device. In other words: there are no assumptions made concerning the underlying hardware responsible for the adjustment purpose itself.
The mathematical model can likewise be used to simulate the effects of the different adjustments on one another, for example the effect of correct focus on convergence, or for example the effect of focus on colour equality (contrast modulation) and chromaticity (gamma).
In accordance with another preferred embodiment, the mathematical model used in the aforementioned methods is improved through an iterative process.
Likewise, in accordance with a preferred embodiment, the calculated model is written to a non-volatile memory for each linked zone. This has the advantage that on subsequent adjustment of this model it can be used as a starting point, instead of having to construct the model on the basis of new digitized values.
When adjustments are to be carried out which are different from those disclosed above, preferably an intelligent sequence of the adjustments is retained given their mutual effect on each other.
The present invention also provides a method for wire-free transmission of information between two or more projectors, at least one of the projectors being provided with at least one camera, and the projectors being mounted in front of a screen. In accordance with the invention, the information is picture information, which is projected via one projector onto the screen and viewed by the camera linked to the other projector. The picture viewed by this camera forms an analog signal which is converted into digitized values via analog-to-digital conversion. Command signals are derived from this which are interpreted by the control unit of the projector linked to the camera in question. The control unit responsible for the interpretation of the command signals is also included in the implementation of the method.
The present invention also provides a method for the decoding of information present in a video signal, using a universal device equipped with a pin as described above. In this method, an analog video signal containing information is applied to the pin. This analog video signal is converted into digitized values via analog-to-digital conversion, from which values command signals are derived which are interpreted by the accompanying control unit. The information in the video signal can, for example, be teletext information.
Preferably, the digitized values in each of the aforementioned methods originate from a universal device in accordance with the invention.